The functional activity and control of the apocrine sweat glands of the scrotum of the ram

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Abstract
When scrotal skin temperature was raised to above 35.3°C, the large glands of the scrotum discharged sweat synchronously at intervals of 2–14 min in eight rams and 9–40 min in one ram. Evaporation of the sweat when the wool on the scrotum was short caused sharp falls in skin temperature of up to 2.6°C; when wool was 18–30 mm long, skin temperature first rose and then fell to either the pre-discharge temperature or just below. Local anaesthesia of the superior perineal nerves abolished the sweat gland response to heat. Although single intravenous injections of adrenaline (1–4 µg /kg) and noradrenaline (1–6 µg /kg) were followed by single sweat gland discharges, bilateral adrenalectomy with replacement of adrenal cortical hormones did not prevent gland discharges in response to heat. The appearance of the first discharge in the adrenalectomized ram was delayed, and the delay was reduced by constant infusions of 0.8–1.0 µg adrenaline /kg/min. Partial lumbar sympathectomy changed the pattern of discharges and reduced the amount of fluid ejected at each discharge. It is concluded that adrenergic sympathetic nerves control the expulsion of sweat in response to heat, but that hormones from the adrenal medulla may also play a part. The control of sweating by cutaneous temperature receptors and its relationship to the possible control exerted by receptors in the brain are discussed in the light of these findings.